Method for drying moulds



Nov. 3, 1970 s. B. RENNERFELT 3,537,136

METHOD FOR DRYING MOULDS Filed Dec. 30. 1968 SVEN BERN'HARD RENNERFELT INVENTOR.

AJMMXLL Attorneys United States Patent Oifice 3,537,186 Patented Nov. 3, 1970 3,537,186 lVIETHOD FOR DRYING MOULDS Sven Bernhard Rennerfelt, Lovhagegangen 4, S-416 56, Goteborg, Sweden Filed Dec. 30, 1968, Ser. No. 787,764 Claims priority, application Sweden, Jan. 16, 1968, 511/68 Int. Cl. F26b 7/00 U.S. C]. 34-21 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method and a device for drying moulds. The object of the invention is to eliminate at such a drying any risk for the occurring of fissures in the mould sand. This has been achieved thereby that the hot air is injected into the mould during a short time period, that the mould then is left to cool during a considerably longer time period, that hot air again is injected into the mould, the latter then left to cool and so on. The device for carrying this method into effect comprises a vertically displaceable fan the movements of which are guided by switches influenced by a cam disk.

The present invention relates to a method for drying moulds by blowing hot air into the mould preferably through the casting gate.

The invention further relates to a device for carrying the method into effect.

The method according to the invention is characterised thereby that hot air is blown into the mould during a short time period, the mould being then left to cool during a considerably longer time before the next blowing in of hot air which is followed by a new cooling period and so on.

The device according to the invention in which the moulds are arranged on a conveyor displaceable from one station to another comprises a vertically displaceable fan, the movements of which are determined by a number of switches acted upon by a cam disk.

The invention will now be elucidated with reference to the annexed diagrammatic drawing. In the drawing:

FIG. 1 shows the device in a side elevation,

FIG. 2 is a view from the opposite side,

FIG. 3 is a view from above, and

FIG. 4 is a plan view of a conveyor.

It is previously known to inject hot air for the drying of casting moulds. However, there is a risk that the mould sand will burst at too fast a 'heating and the mould is thereby made unusable. By means of a mixing of the mould sand with different thinning agents, such as e.g. horse manure, one has tried to prevent the occurring of fissures. However, these thinning agents have caused a formation of gas which is detrimental for the casting and also the smoke formation has been embarrassing.

According to the invention the drying of the moulds is carried out thereby that hot air, preferably at a temperature of 100-300 C., is blown in periodically. A drying process may be carried out as follows: During a period of about two minutes hot air is injected through the charge opening into the mould. The mould is then brought to the side and is given a new treatment during two minutes by means of hot air after about one hour. The course of events is repeated until the desired dryness degree has been achieved in the mould.

The device according to the invention for carrying the method described in the aforegoing into effect comprises an arm 2 swingably carried at one end 1. The arm is provided with a continuous channel 3 housing electric heating coils (not shown). The arm 2 constitutes an elongation of the exhaust opening of a fan 4. The end of the arm remote from the fan is provided with a mouth piece 5. The letter is self-adjusting such that it seals against a mould 6 when lowered against the latter.

Attached to a shaft 7 under the arm 2 is a disk 9 provided with cams 8, these cams intended to influence a number of switches 10. Attached to the shaft 7 is further an eccenter disk 11 which is arranged right under the arm 2 and which has for its object to move the arm up and down. A continuously variable gear 12 drives via an idling wheel the cam disk 9 as well as the eccenter 111. Coupled directly to the shaft 7 is a geared motor 13. The variator 12 is intended to operate all the time and with a very low number of revolutions. The geared motor 13 is intended to be coupled in when there is desired a higher speed of the shaft, i.e. when the eccenter 11 has to move the arm 2. up or down. The cams 8 (only one shown in FIG. 2) are arranged such on the disk 9 that the arm 2 from a swung up position by means of a start of the geared motor 13 and a resulting quick rotation of the eccenter 1.1 is lowered down to a position with the mouth piece 5 in abutment against the mould 6. In this position hot air is blown into the mould. The arm 2 remains in this position, until the cams 8 actuates one of the switches 10 for starting. The geared motor 13 again is started and the eccenter disk 11 swings the arm 2.

Simultaneously with the geared motor 13 also the driving device (not shown) for the conveyor 14 is started, this conveyor 14 carrying the moulds 6. This conveyor takes the shape of an endless conveyor and moves in a 'horizonttal plane. It is provided with a number of disks or tables 15 on which the moulds are arranged. When the conveyor 14 has been moved such a distance that a new mould 6 is situated in front of the mouth piece, the conveyor is stopped and at the same time the arm 2 is moved to a lowered position. The course of events is then repeated until the moulds have reached the desired degree of dryness.

The variator 12 renders possible an exact adjustment of the time period during which the 'hot air is blown into a mould. The time that lapses until one and the same mould again reaches the mouthpiece 5 is of course considerably longer than the injection time proper.

The method described in the aforegoing gives considerable advantages. For the reason that the mould is allowed to cool between two injections of hot air, a tension equilibration takes place in the mould sand and thereby the risk for the occurrence of fissures is effectively reduced. Further, it is at the drying according to the invention sufficient if only a surface layer of the mould sand is dried. As the molten iron is brought to contact only completely dry sand, no evaporation of moisture will take place here and there is obtained a more dense material in the ingot. The moulds 6 do not have to be moved into a furnace for being dried but this drying is carried out at the same place where the casting takes place.

The invention has been described in the aforegoing for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims. Many modifications are possible without departure from the invention. Thus, when the moulds are very big and too heavy to be arranged on a conveyor, the mouthpiece 5 of the drying device may be displaced from one mould to another.

'What I claim is:

1. In a method for drying casting moulds wherein hot air is blown into the mold preferably through the mouldcharging inlet, the improvement comprising the steps of:

(a) injecting the hot air into the interior of the mould for a short time period;

(b) ceasing the injecting of the hot air and letting the mould cool for a time period considerahlylonger attendant greater equilibration of mould tension and' substantially reduced or eliminated risk of fissures.

2. The method as defined in claim :1 wherein the step i of paragraph (a) includes further injecting the hot air specifically via themould-charging inlet.

3-. The method as defined in claim 1, wherein the method includes said periodic injection of the hot air at temperature within the range of from 100-300 C.

4. The methodas defined in claim 1 wherein the short period of time of step (a) is approximately two minutes; and the considerably longer period of time of step (b) is preferably approximately one hour. 2

5. The method as defined in claim 1 further including the conducting of said drying of said mould externally of the normal drying furnace and in the same general area where the casting takes place.

6. The method as defined in claim 1 further including the steps of: I r

(d) providing and utilizing a semi-portable source of drying heat adapted for moving selectively into and out of engagement with andfor efiecting said injection of hot air into the air inlet of a given mould to be dried; 1

(e) mounting a plurality of molds on conveying means with the air inlet exposed to receive the selective injection of hot air, and

(f) conveying them in timed sequence past the source of drying heat during which the alternative steps of heat injection and cooling are carried out.

References Cited UNITED STATES PATENTS 2,385,962 10/1945 Barnett 34-21 2,417,673 3/1947 Barnett et al 34-21 CHARLES SUKALO, Primary Examiner US. Cl. X.R. 1652 

